Figure 3. Comparing larger SWC length versus averaging using the same number of samples.

The simulation in this plot was performed with a TR = 1 sec and estimations were taken over 5 min. In the first panel (a), a window length of h_SWC = 100 sec was selected and the result was not averaged. A fifth-order high-pass Butterworth filter with cut-off 0.01Hz was applied to remove low frequencies of no interest. We can see the existence of spurious SWCs at frequencies not tuned to 1/100 Hz. In panel b), time points were redistributed to have a window length of h_ASWC = 44 sec and an averaging length of g_ASWC = 50 sec. No filter was applied; the simulation used the natural filtering of ASWC described in Figure 2c, but re-adjusted to fit the 0.01 Hz cut-off. In c), the ratio of standard deviations σ_SWC/σ_ASWC has been plot in a logarithmic scale showing that SWC exhibit higher artifact power than ASWC at frequencies higher than the cut-off 0.01 Hz.